The invention relates generally to packaging and sealing apparatus for packaging products inside plastic bags. More particularly, the invention provides a bag making and packaging machine that includes sealing mechanisms for sealing a tubular packaging material in longitudinal and lateral directions to make bags with a packaged material packaged inside the bags.
Vertical-type bag making and packaging machines are known for packaging materials such as food products inside plastic bags. For example, one type of packaging machine makes bags by shaping a sheet-like film packaging material into a tubular shape with a former and a tube, and then heat sealing overlapped longitudinal edges of the tubular packaging material with a longitudinal sealing mechanism. The packaged material is then filled into the tubular packaging material. Bags will ultimately he formed from this tube. A portion across the upper end area of one bag and the lower end area of another following bag is sealed by a lateral sealing mechanism, and the laterally sealed portion is then cut across its center by a cutter.
Mechanisms that press a pair of mutually opposed seal jaws against a tubular packaging material are frequently employed to heat and pressure seal the material. In systems in which the seal jaws merely reciprocate, i.e., ones in which the sealing of the packaging material is performed at only one location (a line), transportation of the packaging material must stop for the time required to form the seal. Such machines are sometimes designed, therefore, so that each of the seal jaws draws a D-shaped locus. In that case, the sealing time can be made long enough by moving the seal jaws to follow the tubular packaging material while it is transported continuously through the machine.
To make the seal jaw draw a D-shaped locus, a mechanism can be used with a grooved cam for restraining the inside and outside of a cam follower. In such a device, however, the drive member slides in sliding contact with the cam follower and the seal jaw, and this gives rise to problems of wear and durability at the points of sliding contact, especially in high speed operation.
Other mechanism have thus been devised, in which sealing mechanisms of special construction draw non-circular loci including D-shaped loci, but in which such sliding contact is largely avoided. In such constructions, though, the size of the bags that can be sealed is often restricted. Increasing the size of the bags that can be handled requires an excessive and troublesome increase in the size of the parts of the corresponding mechanism. As a result, a large space is occupied by the sealing mechanism and the machine itself may thus be excessively large.
Such mechanisms also require a large number of parts with a complicated construction, and they too sometimes suffer problems of limited durability. An additional problem often exists, moreover, where the sealing faces are restrained by cams or other elements that define their loci of motion. In particular, the sealing elements are restrained and thus cannot move away if a piece of the packaged material is caught between the sealing faces. As a result, the packaged material may be crushed or the sealing elements themselves may be damaged, especially when hard materials are being packaged with the machine.
A need exists, therefore, for improved bag-making and packaging machines of simple and reliable construction. To the extent possible, such machines should provide high speed bag making and packaging, including the formation of reliable seals in the packaging material. Such machines should be durable (so that excessive sliding contact between the machine""s parts should be avoided). The machine should resist damage either of the packaged material or to the parts of the machine itself, and the machine should not be overly large or of overly complex construction.
The invention is embodied in a lateral sealing mechanism and in bag making and material packaging machines that use such lateral sealing mechanisms. A lateral sealing mechanism according to the invention may include at least one sealing element that is operable to contact and seal a tubular packaging material. The seal may be formed, e.g., by applying heat from the sealing element to the tubular packaging material to form a heat seal.
The sealing element is supported on a support mechanism. The support mechanism includes a cam follower that engages with a cam face on a cam. The support mechanism is movable to contact the sealing element with the packaging material, and then to separate the two after the seal is formed. The support mechanism is supported on a rotary shaft so that the support mechanism rotates around the shaft. The lateral direction drive mechanism moves the cam and the rotary shaft together in a direction perpendicular to the rotary shaft as the support mechanism rotates about the shaft.